A separation membrane technology is utilized in various fields inclusive of a water treatment field such as drinkable water production, water purification treatment and wastewater treatment, a food industry field, and so on. For example, in the water treatment field such as drinkable water production, water purification treatment and wastewater treatment, separation membranes have been used for the purpose of removal of impurities in water as alternatives to conventional sand filtration and coagulating sedimentation processes. In the waste water treatment field, an activated sludge membrane filtration treatment process using a separation membrane for the separation of a flocculated sludge and water from each other from a microbial consortium called an activated sludge is widely adopted. In addition, in the food industry field, a separation membrane is used aiming at separation and removal of yeast used for fermentation or concentration of a treatment stock solution.
Recent progress of technologies in various fields including chemical industry is notable, and the separation membranes are required to have much more improvements in corrosion resistance, such as endurance against a high temperature and a high pressure, separation of a liquid mixture containing an organic solvent, an acid, or an alkali, etc.
Heretofore, as separation membranes coping with the above-described liquid mixture, sintered metal filters or ceramic filters having high specific strength at a high temperature, materials based on carbon fibers, and the like have been generally used.
However, in the case of sintered metal filters, there is a concern that the constituent metals are eluted, and there is a case where the acid resistance is insufficient. In addition, in the case of ceramic filters, though the acid resistance is sufficient, there is a concern that particles are eluted, and in particular, there is a case where Si accumulates, thereby clogging the filter, the piping, or the like. Furthermore, the ceramic filters involved such a problem that the filtration efficiency is low because handling is difficult, whereby modulation thereof is difficult.
Meanwhile, a composite separation filter described in Patent Document 1 has excellent characteristic features, such as endurance against a high temperature, good corrosion resistance, etc., in view of the matter that it has carbon fibers as a substrate. In addition, Patent Documents 2 and 3 disclose hollow carbon membranes. Patent Documents 4 and 5 disclose flat membrane type carbon membranes.